The present invention concerns electromagnetic compatibility measurements and pertains particularly to traceable, self-contained, programmable frequency source for performing alternate test site and open area test site comparisons.
In order to comply with various regulations and to satisfy performance requirements of consumers, electronic equipment are required to conduct and radiate less than a maximum limit of unwanted electromagnetic energy and are required to have a certain level of immunity against other electromagnetic sources. Measurement methods are supplied in standards such as IEC 1000-4-3, IEC 1000-4-6, ANSI C63.4, CISPR 22.
The coupling of energy to and from a system is not only influenced by the design of the system but also can be affected by the characteristics of the site used to test the equipment.
Over the past 20 years there have been several site sources developed in an attempt to compare electromagnetic interference (EMI) measurement sites, both for radiated EMI signals and for conducted EMI signals. Each of these have one major drawback, the amplitude of the signal output could not be reproduced with any degree of accuracy from unit to unit. Some of the product available could specify +/-0.5 dB unit-to-unit variation if they were built using the same "lot/batches" of components. Once a unit failed the reference was lost. One unit of a reproducible type was developed in 1986 by Hewlett-Packard Company, having a business address of 3000 Hanover Street, Palo Alto, Calif. 94304. However, this unit was lost in transit in 1996.